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Torsion test machine design

In structural design, torsional moment may, on occasion, be a significant force for whichprovision must be made. The most efficient shape for carrying a torque is a hollow circular shaft;extensive treatment of torsion and torsion combined with bending and axial force is to be foundin most texts on mechanics of materials.When a simple circular solid shaft is twisted, the shearing stress at any point on a transversecross-section varies directly as the distance from the center of the shaft. Thus, during twisting,the cross-section which is initially planar remains a plane and rotates only about the axis of theshaft.Torsion members are frequently encountered in structures and machines. A structural membermay need to resist torques induced by a load, such as wind or gravity. Machinery examplesinclude motor vehicle drive shafts, torsion bar suspensions, ship propeller shafts, and centrifugalpump shafts. In the analysis of torsionally loaded members, we are primarily concerned with thetorsion stress and the angle of twist on the shaft. In our laboratory experiment, the primaryemphasis is on the recognition of torsion on the usual structural members, how the torsionstresses may be approximated and how such members may be selected to resist torsion effects.

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Design Torsion Machine 20111. Introduction In structural design, torsional moment may, on occasion, be a significant force for whichprovision must be made. The most efficient shape for carrying a torque is a hollow circular shaft;extensive treatment of torsion and torsion combined with bending and axial force is to be foundin most texts on mechanics of materials.When a simple circular solid shaft is twisted, the shearing stress at any point on a transversecross-section varies directly as the distance from the center of the shaft. Thus, during twisting,the cross-section which is initially planar remains a plane and rotates only about the axis of theshaft.Torsion members are frequently encountered in structures and machines. A structural membermay need to resist torques induced by a load, such as wind or gravity. Machinery examplesinclude motor vehicle drive shafts, torsion bar suspensions, ship propeller shafts, and centrifugalpump shafts. In the analysis of torsionally loaded members, we are primarily concerned with thetorsion stress and the angle of twist on the shaft. In our laboratory experiment, the primaryemphasis is on the recognition of torsion on the usual structural members, how the torsionstresses may be approximated and how such members may be selected to resist torsion effects.1.1 ObjectivesThe torsion test is used the most to evaluate the shear forces and resultant stresses on the circularbar. This test demonstrates the state of pure shear stress in the rod twisted. Based on Mechanicsof Materials, equations to evaluate the different mechanical properties of metals were used in thismachine design. By experimental mechanics, the torsion state of the specimen was obtained tomeasure the different mechanical properties such as the yield shear stress, the ultimate shearstress, and the shear modulus. Analysis provides cognitive relations between shear strain andtoque. In this report the design layout and the concept of torsion machine design are included inthis report. Laboratory, specimens in torsion were subjected to force applied. After themeasurement, different mechanical properties were determined from the equation based on theMechanics of Materials. Analytical results based on the three different methods were comparedto the data measured during the experiment.1.2 THEORYFrom the general torsion theory for a circular specimen. T G     J L rWhere, 4T = Applied Torque ……………………………………… Nm or lbf in MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 20113 Maintenance3.1 Calibrating a Torque Wrench  Step 1 – Marking PointsUse a pencil or marker to mark the center point of thewrench head on the back of the torque wrench.  Step 2 – Taking the MeasurementsNext, take the measurements. Measure the center point tothe point where you apply the most pressure when youuse the wrench. Write this measurement down asdistance one. If the wrench measures in inch pounds,write down this measurement in inches as distance one.If the wrench measures in feet pounds, write down the distance measurement in feet.  Step 3 – Using the WeightsUse the vise to horizontally clamp the wrench bit. Hang a twenty pound weight from the wrenchhandle using the string.  Step 4 – Total MeasurementsMove the weight along the wrench handle until it measures at 40 foot pounds or 480-inchpounds. Measure the distance from the center point on the wrench head to the string and writethis measurement down as "distance 2."  Step 5 – Calibration RatioUsing a calculator, divide distance 2 by distance 1 and this will give you the calibration ratio.The ratio is the difference between the wrench settings and the force needed to get a “click” atthat setting.  Step 6 – Setting Torque WrenchSet your torque wrench for a specific application. You can do this by taking the torque of the boltand multiplying the required torque of the bolt by the calibration ratio.Torque wrenches should be calibrated annually. Expect this to cost about $25 to $35 if you takeyour torque wrench to a decent shop to be calibrated properly. You can purchase a digital adapterfor torque which lets you calibrate the wrench yourself. The digital torque costs around $50.Adjustment and repair of the torque wrench usually runs around $15 per quarter hour.  Step 7 - StorageKeep the torque wrench lubricated and clean. After each use, always turn the scale back to zeroto prevent the spring inside the wrench from setting and causing the calibration to drift. Thetorque wrench is the only practical way to measure bolt tension. Proper maintenance ensures alonger life for the torque wrench.3.2 Calibrating a laser distance sensor  Step1 Switch on the calibration power meter and place it on an optical bench. The calibration powermeter will come with a broadband light source which is guided through an optical fiber. Once 7switched on, the calibrated power of the light source will be displayed on its display.  Step 2 MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 2011Place the optical fiber from the calibration meter into the sensor of the laser meter, and take noteof the measured power on both devices. The power displayed will be measured in Watts (W) ormilli-Watts (mW).  Step 3Determine the calibration factor by dividing the value displayed on the calibration power meterby the number shown on the laser meter. The laser meter has now been calibrated and can beused on other light sources to determine the power. The measured power now needs to bemultiplied by the calibration factor determined above to obtain the correct value.3.3 Lubricating the gearWhen used in a gearbox the lubricant provides two primary two benefits: to lubricate the teethand to remove heat generated from the gear operation. The lubricant is also often used forlubricating the various bearing found in the gearbox. If the correct lubricant is selected for use ina gear system it will provide slip-free power transmission at high mechanical efficiency, withgood reliability, low maintenance, and long life.To meet the lubrication needs of modern enclosed industrial gear drives, a gear lubricantmust possess the following key performance properties: Thermal and oxidative stability Thermal durability Compatibility with seal materials Protection against excessive gear and bearing wear High-temperature extreme pressure protection (EP gear oils) Gear and bearing cleanliness Emulsibility characteristics Rust and corrosion protection, especially to yellow metal components Antifoaming characteristicsGrease Lubrication: Grease lubrication is suitable for any gear system that is open or enclosed, so long as it runs at low speed. The grease should have a suitable viscosity with good fluidity especially in an enclosed gear unit. Grease is not suitable for high loads and continuous operation and there is virtually not cooling effect. The must be sufficient grease to ensure the gear teeth are lubricated but an excess can result in viscous drag and power losses. 8 MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 20114.1 Date used for designTo find out what is maximum torque will be required and how much rotation will be resultantfrom the testing of material, we should study and apply the equation to find the angle of twist ofeach material and required torqueTable 2: Shear strength and shear modulus for selected materials material shear strength MPa modulus of rigidity GPa96% alumina 330304 stainless steel 186 73Copper 42-220 44Aluminum 30-483 26Sn63 solder 28860 6epoxy resin 10 – 40Looking to the table 2 in more details we can find that if we compare steel, copper andAluminum we can find that 304 steel has the higher of Modulus rigidity with 73 Gpa.From that we can indicate the larger torque will be required for our design.To calculate the J value we should use the following equation = 981.7477mm4So from that we can notes that J ,r and L are same for all specimens J is 981.7477mm4 r= 5 mmand L= 200We can calculate the to find the unknowing data such as angle of twist and torque for steel is =3.72 N/m3 for cooper is =8.4 N/m3 for aluminum is =6 N/m3by having the value of =that will give us angle of twist = 0.102 rad =0.1326 rad=7.59 degree 10 =0.0381 rad =0.199644 rad=11.439 degree MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 20115 Main part and function tableComponent Name Function PictureFrame To hold and carry the weight of all componentSafety guard To protect from injury due to break of metalTorque wrench  To generate enough torsion force to twist the material.  To measure the torque 13 MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 2011Drill chock To hold the specimen in both the moving end and fixed endRack and pinion To change thegear rotary motion of the shaft in to linear motion to measure the angle of twistLaser distance To measure thesensor displacement of the rack gear to represent the angle of twist 14 MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 20116.2 Measuring the angle.By converting the rotating motion oftwist to linear motion, we canmeasure the angle of twist. This doneby calculation how much will beresulted in linear motion when fullturn of twist is there.To do so rack and pinion gear isused. the size of pinion diameter is50mm then the movement of onerotation is π×D 157mm. and we needat least to make 5 rotation. Therefore,the diameter should be less than 50.we can find other pinion gear withdiameter of 20 mm then themovement of one rotation is π×D=62.8mm . from that we can noteseach 1 mm movement rack gearmean that the pinion rotate 5.73 degree. On other hand. Toread 0.5 degree rotation of twist, the rack should move 0.09mm which is close to 0.1mm. the total linear motion will be62.8×6 =376.8. the device used to measure the rotation canbe laser sensor.The following picture show the idea of using laser sensor toknow the angle of twist 16 MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 2011The diametric pitch is number of teeth divided by the pitch diameter.The pitch diameter we have is 20mmFrom table 8-3 standard modules we find the following 17 MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 20116.3 Specification of laser sensorThe MRL-ML1 is a short range laser measurement sensor fromMetrology Resource Co. with an accuracy of ± 3.0mm @ 2SIGMA and a range of 0.05m to 30m.The MRL-ML1 Laser Distance Sensors are the new generation ofMRC devices that are compact and robust distance measuringmodules designed to meet the demands of the industrialmeasurement market.Principles of OperationThe MRL3 device is a phase shift laser measurement device thatcompares the outgoing and returning wave signals to determine the distance to a target. Thesefrequency waves are timed to an internal clock to measure the time it takes for the laser light togo out and return to the sensor. This phase shift is often calibrated based on ambient lightingconditions and temperature.6.4 Griping device to hold specimenA drill chock can be used for this purpose. Of drillchock will be fixed to the rotating shaft with piniongear and torque wrench. The other one will be notrotating fixed on the other side on the frame. 20 MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 2011The following diagram shows the assembly of identified part on the topAssume that the rack gear has moved 10 mm linearly what is the angle of twist. by knowing thatthe circumference of the pinion is 62.8 mm. That represent 3600 then the 10mm displacement is 0 21 MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 2011The following graph illustrates property of material comparing the strength of material with itsprice.The graph indicated that the composites materials are more expensive than metal. Moreover 23metal can be used for application used higher load than in composite MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 2011The following graph show the strength of metal and alloy Vs the cost.As it can be seen from metal and alloy, high allow steel has maximum strength of 3000 MPawith cost of 8 euro per kilogram. However mild steel has strength of more than 100 Mpa withcost of 0.5 euro per kilogram.8 Ease of safe operation8.1 Equipment and ClothingAvoid wearing long flowing clothes. Tie up long hair. Wear protective equipment such as a dustmask, gloves, eye protection, ear mufflers, jacket and boots that provide good grip on the floor.8.2 Surrounding AreaMake sure the area around the machine is free of clutter and you have sufficient space to work.Do not work in poorly lit conditions or in positions that are uncomfortable to you. Notify asupervisor of such problems promptly. The machine must be positioned on a stable surface andmust be a suitable distance away from you. Position yourself in a comfortable manner so thatyou do not have to reach out or bend.8.3 Starting a MachineBefore starting a machine, check the machine guards and ensure they all fit and are in place.Ensure that any keys or wrenches are removed so they do not fly out and hit you or another 24person nearby. Never operate a machine if you notice loose parts, unusual sounds or vibrations.To avoid electric shocks, you must ensure that the machine is properly grounded. MTRX-322 | HTC, Abu Dhabi

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Design Torsion Machine 20118.4 Operating a MachineNever let yourself be distracted from the task at hand. If somebody interrupts you, turn off themachine before you start a conversation. Never interrupt or startle a co-worker who is handling amachine. Always use feeding and holding tools to push objects toward the machine or to clampthem in place. Never attempt to remove a blockage or stalled part without first turning themachine off and putting the safety locks in place. You must never leave a machine unattendedwithout turning it off. 25 MTRX-322 | HTC, Abu Dhabi